Biophysics最新文献

Particles of medium- and high-molecular-weight chitosans and carboxymethyl chitosan were obtained with or without ascorbic acid. Methods were developed to obtain complexes of these particles with the plant protease papain. It was found that the activity of papain complexes with particles of carboxymethyl chitosan is significantly higher compared to its complexes with particles of chitosan. At the same time, complexes with particles of chitosan and carboxymethyl chitosan obtained with ascorbic acid showed higher values of proteolytic activity than complexes with polysaccharide particles obtained without it. Using molecular docking, it was found that amino-acid residues of papain interact with both chitosan and carboxymethyl chitosan mainly by forming hydrogen bonds and van der Waals interactions. In addition, ascorbic acid molecules and both types of polysaccharides interact with amino-acid residues from the active site of papain, Cys25 and His159, which probably contributes to an increase in the activity and stability of the enzyme in complexes with particles of chitosans and carboxymethyl chitosans, including due to the fact that ascorbic acid prevents the oxidation of the thiol group of papain, which is responsible for the act of catalysis.

Predicting yield-related traits such as the thousand seed weight (TSW) allows researchers to develop varieties that achieve maximum efficiency and value under changing climate conditions. In this paper, we propose a Markov network model for predicting the important phenotypic TSW trait in chickpea genotypes using pre-selected single nucleotide polymorphisms and weather data for 5 days before and 20 days after sowing, such as minimum and maximum temperatures, precipitation, humidity, infrared radiation, and daylength. The constructed model predicts the TSW trait with high accuracy; the Pearson correlation coefficient is 0.83.

The radioprotective properties of copper chlorophyllin, riboxin (inosine), and trolox (a water-soluble form of vitamin E) were studied after irradiation of outbred male mice of the ICR (CD-1) SPF category with X-ray radiation at a dose of 6.5 Gy. The test substances were administered intraperitoneally to mice an hour after irradiation; the drugs were then administered 3 more times at daily intervals. The volume of administered drugs was 0.32 mL. The dosages for each administration were trolox at 200 μg/g body weight; copper chlorophyllin, 50 or 100 μg/g; and riboxin, 200 μg/g. Mice were euthanized 4 days after irradiation. The radioprotective efficacy was assessed based on 30-day survival and on the basis of the following indicators 4 days after irradiation: body weight, weight of the thymus and spleen, hematological indicators (leukocytes, lymphocytes, monocytes, granulocytes, erythrocytes, platelets, hemoglobin, hematocrit, and thrombocrit), the number of nucleated cells in the bone marrow, and the content of thiobarbiturate-reactive products in the liver. Irradiation caused a decrease in the mass of the thymus and spleen, the contents of leukocytes and platelets in the blood, and the number of nucleated cells in the bone marrow. The studied substances, when using the given application scheme, did not contribute to an increase in these parameters. Irradiation led to an increase in the content of thiobarbiturate-reactive products in the liver of mice, which is a marker of lipid peroxidation caused by it. All studied substances contributed to a decrease in this criterion, except for chlorophyllin administered at a dosage of 100 μg/g (total dosage 400 μg/g). However, an increase in survival compared to the irradiated control group occurred only in this case. Trolox and riboxin contributed to a decrease in the content of end products of lipid peroxidation in the majority of mice from the corresponding group. However, in some of them this effect was not observed at all. The use of copper chlorophyllin in the regimen we used led to the appearance of signs of chemical poisoning in mice. We explain this by its manifestation of toxic properties due to the presence of a copper atom in its molecule. It seems promising to repeat the study using a chlorophyll derivative that does not contain copper.

The subunits of the voltage-gated potassium channels Kv1.1 and Kv1.2 can form both homo- and heterotetrameric channels in cells, the functional properties and localization of which differ significantly. Confocal microscopy based on Förster resonance energy transfer was used to study the formation of Kv1 channels during the co-expression of Kv1.1(S369T) and Kv1.2(S371T) subunits in mouse neuroblastoma cells, which were fused with the fluorescent protein mKate2 and TagCFP, respectively, and had enhanced membrane expression due to mutation. It was found that TagCFP-Kv1.1(S369T) and mKate2-Kv1.2(S371T) effectively formed heterochannels that were localized both in the plasma membrane and in the cytoplasm of cells. In the absence of the S369T mutation, heterochannels did not integrate into the plasma membrane, which indicated the need for auxiliary factors for the transfer of native heterochannels into the membrane. In addition to heterochannels, homotetrameric channels were formed in Neuro-2a cells; however, the efficiency of heterochannel formation was much higher.

The effect of astaxanthin, diethyldithiocarbamate and their combined use on cell proliferation was studied on the culture of mouse N1E-115 neuroblastoma (clone C-1300). There is evidence of the anticancer effect of astaxanthin in various types of tumor cells. Diethyldithiocarbamates are used as additional drugs in chemotherapy. The use of non-toxic drug complexes is a new strategy for the treatment of oncological diseases. We have shown that the effect of diethyldithiocarbamate and astaxanthin, both individually and when used together, caused inhibition of proliferation and induction of differentiation of mouse N1E-115 neuroblastoma cells. Western blot analysis revealed that the combination of the drugs increased the expression of CHOP protein (a marker of the endoplasmic reticulum) and proapoptotic protein BAX, and reduced the expression of antiapoptotic protein Bcl-2, which may indicate the start of the apoptotic cascade. At the same time, the use of diethyldithiocarbamate alone caused a decrease in both Bax and Bcl-2 levels and did not affect CHOP protein expression. Apparently, astaxanthin modifies the effect of diethyldithiocarbamate when they are used together.

The possibilities of quantitative analysis of weak signals from cells of biochip arrays fixed on a substrate, the fluorescence of which is comparable in intensity to the fluorescence of the substrate, were investigated using a specially designed wide-field digital microscope, a highly sensitive biochip analyzer. In the spectral range of cyanine dye Cy5 (λ_ex = 645 nm, λ_em = 665 nm), the relative levels of intrinsic fluorescence of the surfaces of a number of materials that can serve as substrates for biochip matrices used in medical diagnostics were evaluated. It was shown that the analyzer on a substrate of black polybutylene terephthalate (black crastin) allows detecting the fluorescence of 3 and more Sy5 dye molecules/µm² on its surface.

Nanosized materials are widely used in biomedical nanotechnologies, but the mechanisms of toxic effects of metal and nonmetal nanoclusters remain unclear. The aim of this work is to evaluate the size characteristics and mechanisms of toxic action of silver, selenium and cobalt nanoparticles at the level of isolated mitochondria. Using the laser ablation method, silver (rounded, ~10–20 and ~50 nm), cobalt (cubic and prismatic, ~100–200 nm) and selenium (spherical, ~20–30 and 135–180 nm) nanoparticles with different spectral characteristics and capable of forming conglomerates were obtained. Silver, cobalt, and selenium nanoparticles (0.1–10 μg/mL) effectively inhibited the respiratory activity of isolated rat liver mitochondria by disrupting the coupling of oxidation and phosphorylation, which was accompanied by a drop in the mitochondrial membrane potential. The uncoupling effect of nanoparticles may be associated with the transfer of electrons from the electron transport chain of mitochondria to the positively charged surface of nanoparticles and depends on the size and material of the nanoparticles.

In the present study, we functionally analyzed the c.67A>T (p.Met23Leu) missense-mutation in the KCNE2 gene of potassium channel Kv11.1 complementary subunit identified in a patient with asymptomatic QT interval prolongation on electrocardiogram. We artificially introduced this substitution into the plasmid encoding the KCNE2 subunit and expressed the mutant gene in Chinese hamster ovary cells together with the wild-type Kv11.1 channel gene to evaluate the effect of the mutation on I_KR current parameters. We used a comprehensive approach including the study of the integrated I_Kr current using whole-cell patch clamp method. The study showed that the c.67A>T mutation (p.Met23Leu) is a gain-of-function type, but the current density carried by Kv11.1 channels is significantly reduced. Fluorescence microscopy showed impaired trafficking of a channel coexpressed with the mutant subunit to the cell surface. We applied molecular modeling to examine the location of the mutant subunit relative to the membrane.